This invention pertains the field of underground construction, and more particularly to the use of construction lasers for alignment of underground structures, such as conduits. When such laser units are used, it is necessary to establish a plumb or vertical line directly above the laser unit. If there is no free vertical space above the laser, such as inside a manhole having an offset cover, then it is necessary to measure over to the laser from some arbitrary point, for example, by using a ruler, and thus inaccuracies in alignment can result.